1. Field of the Invention
The present invention relates to a method and a device for positioning a columnar structure.
2. Background Art
When a coating is applied to an outer circumference of a columnar structure with a curved surface such as a cylindrical column and an elliptic cylindrical column (e.g. a honeycomb structure and a diesel particulate filter), most coating works rely on manual labor. When labor is relied upon, skilled workmen are required and manual works take a large amount of man-hours. In addition, a low efficiency must be accepted in order to obtain a large amount of appropriately coated products. This step is a bottleneck in some manufacturing processes.
A device and a method have been proposed for coating an outer circumferential surface of a columnar structure that can apply a thin and uniform coating to the outer circumferential surface of a columnar structure and thus can prevent flaws, peeling, and occurrence of cracks in the coated part after coating and during drying (see Japanese Patent Applications Laid-open No. 2004-141708 and No. 2004-141709).
In this method, a positioning device as shown in FIGS. 4(a) and 4(b), for example, is used for positioning the central axis of the columnar structure which is mounted on a seat of the outer circumferential surface coating device. As shown in FIG. 4(a), this positioning device can cause the central axis of the columnar structure 1 to approximately coincide with the central axis of a seat 3 by moving the columnar structure 1, while causing centering boards (positioning fixtures) 21 and 21 on either side to slide in relation to the columnar structure 1 mounted on the seat 3 by a driving force (servo+air cylinder) and at the same time, causing the centering boards 21 and 21 to abut on the columnar structure 1 (see FIG. 4(b)). The area of the centering board 21 coming in contact with the outer circumferential surface 1a has a configuration conforming to the shape of the outer circumferential surface 1a. In the case of a cylindrical columnar structure 1, for example, a centering board (positioning fixture) 21 having a circular arc 22 as shown in FIG. 5 is used.
However, in the positioning device shown in FIGS. 4(a) and 4(b), it is difficult in practice to cause the centering boards (positioning fixtures) 21 and 21 on either side to slide and simultaneously abut on the columnar structure 1. In addition, since the device does not possess a means for maintaining a fixed distance between the central axis of the columnar structure 1 and the central axis of the seat 3, when either of the centering boards (positioning fixtures) 21 and 21 abut on the outer circumferential surface 1a, the central axis of the columnar structure 1 is shifted toward the centering board 21 that has first come in contact with the outer circumferential surface 1a, thereby unduly impairing precision of coincidence of the central axis of the columnar structure 1 and the central axis of the seat 3.
Moreover, since the positioning device shown in FIGS. 4(a) and 4(b) has the area coming in contact with the outer circumferential surface 1a of the centering board 21 in the shape conforming to the outer circumferential surface 1a of the columnar structure 1 (circular arc 22) as shown in FIG. 5, that is, since these parts abut face-to-face, the precision of coincidence of the central axis of the columnar structure 1 and the central axis of the seat 3 fluctuates according to the circumferential configuration of the columnar structure 1.
If the precision of coincidence of the central axis of the columnar structure 1 and the central axis of the seat 3 is impaired for these reasons, in the case in which the device is applied to an outer circumferential surface coating device shown in FIG. 6, for example, a clearance w may become too small in some area and, when the outer circumferential surface 1a of the columnar structure 1 comes in contact with a leveling board 10a, the coating may produce flaws or be peeled off because the leveling board 10a is made of a hard material such as SUS or ceramics. When the clearance w between the outer circumferential surface 1a of the columnar structure and the leveling board 10a is excessively enlarged in order to avoid the contact, the coating thickness unduly increases and cracks may be produced in the coating during drying.
If there are variations in the coating thickness of the resulting columnar structure, not only properties such as thermal shock resistance, isostatic strength, thermal stress, mechanical stress, and the like are impaired, but also cracks are easily produced in thick portions of the coating when forced drying is applied, resulting in poor productivity.
The present invention has been achieved in view of the above-described problems of the related art. An objective of the present invention is to provide a method and a device for positioning a columnar structure that can promote properties of the resulting columnar structure (ceramic honeycomb structure), such as thermal shock resistance, isostatic strength, thermal stress, mechanical stress, and the like, and can exhibit improved productivity due to excellent drying performance of the coated areas by approximation of the central axis of the columnar structure and the central axis of the seat, thereby flattening the coating thickness when a coating is applied to the outer circumferential surface of the columnar structure.